Unexpected null value error on even simple widget

[abhilashsajeev]

I am writing this widget

import 'package:flutter/material.dart';
import 'package:marquee/marquee.dart';

class TestScreen extends StatelessWidget {
  const TestScreen({super.key});

  @override
  Widget build(BuildContext context) {
    return Container(
      child: SizedBox(
        height: 50,
        child: Marquee(
          text: "Hello to this is sample marquee",
          crossAxisAlignment: CrossAxisAlignment.center,
          blankSpace: 20,
        ),
      ),
    );
  }
}

Eventhough the app runs and displays the marquee in terminal following error is shown

Error: Unexpected null value.
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/priv
ate/ddc_runtime/errors.dart 266:49      throw_
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/priv
ate/ddc_runtime/operations.dart 528:63  nullCheck
packages/flutter/src/widgets/scroll_position.dart 141:49
get minScrollExtent
packages/flutter/src/widgets/scroll_position.dart 668:18
[_updateSemanticActions]
packages/flutter/src/widgets/scroll_position.dart 984:5
notifyListeners
packages/flutter/src/widgets/scroll_position.dart 384:5
forcePixels
packages/flutter/src/widgets/scroll_position_with_single_context.dart 197:7
jumpTo
packages/flutter/src/widgets/scroll_controller.dart 172:15
jumpTo
packages/marquee/marquee.dart 548:23
<fn>
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patc
h/async_patch.dart 84:54                runBody
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/patc
h/async_patch.dart 123:5                _async
packages/marquee/marquee.dart 544:51
<fn>
packages/flutter/src/scheduler/binding.dart 1175:15
[_invokeFrameCallback]
packages/flutter/src/scheduler/binding.dart 1113:9
handleDrawFrame
packages/flutter/src/scheduler/binding.dart 1015:5
[_handleDrawFrame]
C:/b/s/w/ir/cache/builder/src/out/host_debug/flutter_web_sdk/lib/_engine/engine/platfor
m_dispatcher.dart 1168:13               invoke
C:/b/s/w/ir/cache/builder/src/out/host_debug/flutter_web_sdk/lib/_engine/engine/platfor
m_dispatcher.dart 219:5                 invokeOnDrawFrame
C:/b/s/w/ir/cache/builder/src/out/host_debug/flutter_web_sdk/lib/_engine/engine/initial
ization.dart 195:45                     <fn>
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/priv
ate/ddc_runtime/operations.dart 334:14  _checkAndCall
C:/b/s/w/ir/cache/builder/src/out/host_debug/dart-sdk/lib/_internal/js_dev_runtime/priv
ate/ddc_runtime/operations.dart 339:39  dcall

Why is this happening and how to resolve this?

[abhilashsajeev]

@MarcelGarus

[MarcelGarus]

Interesting. I actually can't reproduce this – it works for me (this is the example application from the example directory with your widget as the body):

Can you maybe post your entire example including the main function?

[abhilashsajeev]

@MarcelGarus I use a getx main function. very normal ones

import 'dart:math';

import 'package:flutter/services.dart';
import 'package:window_manager/window_manager.dart';

import 'constant/route_constant.dart';
import 'ui/view/second_home.dart';
import 'package:flutter/material.dart';
import 'package:get/get_navigation/src/root/get_material_app.dart';

import 'constant/get_pages_constant.dart';

void main() async {
  try {
    WidgetsFlutterBinding.ensureInitialized();
    SystemChrome.setPreferredOrientations([
      DeviceOrientation.landscapeRight,
      DeviceOrientation.landscapeLeft,
    ]).then((value) => runApp(MyApp()));
    await windowManager.ensureInitialized();
    WindowOptions windowOptions = const WindowOptions(fullScreen: true);
    windowManager.waitUntilReadyToShow(windowOptions, () async {
      await windowManager.show();
      await windowManager.focus();
    });
  } catch (e) {}
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return GetMaterialApp(
      title: 'MyApp',
      debugShowCheckedModeBanner: false,
      theme: ThemeData(
        primarySwatch: Colors.deepPurple,
        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      getPages: getPages,
      initialRoute: RouteConstant.homeScreen,
      home: const SecondHome(),
    );
  }
}

Also when I try to render marquee text dynamically, (Wrapped in OBX) the error throws

[ERROR:flutter/runtime/dart_vm_initializer.cc(41)] Unhandled Exception: Null check operator used on a null value
#0      ScrollPosition.minScrollExtent (package:flutter/src/widgets/scroll_position.dart:141:49)
#1      ScrollPosition._updateSemanticActions (package:flutter/src/widgets/scroll_position.dart:668:18)
#2      ScrollPosition.notifyListeners (package:flutter/src/widgets/scroll_position.dart:983:5)
#3      ScrollPosition.forcePixels (package:flutter/src/widgets/scroll_position.dart:384:5)
#4      ScrollPositionWithSingleContext.jumpTo (package:flutter/src/widgets/scroll_position_with_single_context.dart:202:7) 
#5      ScrollController.jumpTo (package:flutter/src/widgets/scroll_controller.dart:172:16)
#6      _MarqueeState.initState.<anonymous closure> (package:marquee/marquee.dart:548:23)
#7      SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1289:15)
#8      SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1227:9)
#9      SchedulerBinding._handleDrawFrame (package:flutter/src/scheduler/binding.dart:1076:5)
#10     _invoke (dart:ui/hooks.dart:145:13)
#11     PlatformDispatcher._drawFrame (dart:ui/platform_dispatcher.dart:338:5)
#12     _drawFrame (dart:ui/hooks.dart:112:31)